The primary mission of the Protein Core is to provide protein production and purification services to the three components of this program project grant. The core will be responsible for building expression vectors, expressing and purifying recombinant proteins, submitting the proteins for production of antibodies by commercial vendors, and carrying out initial evaluation of antibodies generated to these proteins. The core will also maintain a range of bacterial and eukaryotic expression vectors and cell lines for protein production. Finally, the core will store and distribute polyclonal and monoclonal antibodies raised against the various proteins and domains purified by the core. These services will provide support to all three projects within the program. The availability of recombinant proteins will be vital to achieve the goals of all three projects within the program. Because the entire program revolves around the common theme of Notch signaling, the molecules studied in the three project components are frequently shared and overlapping. Therefore, proteins generated by the core facility can be distributed to all three project components, providing reagents to each group without duplication of effort. Similarly, the antibodies generated for detection of proteins produced by the core will also be used by all three projects. The location of the core facility, adjacent to the Blacklow laboratory where there is a wealth of existing skill in the expression and purification of recombinant proteins for biochemical and structural studies, will bring additional direct benefit to the projects to be carried out in the Aster and Pear laboratories, where there is less expertise in protein production.